Osha River

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Course of the Osha ( Оша ) in the catchment area of the Irtysh (yellow)

The Osha (Russian Оша ) is a 530 km long left tributary of the Irtysh River in the West Siberian Plain (Russia).

The Oscha entfließt good 20 km north- west of the city Tjukalinsk the Koscharasee, which in turn is fed by the 44 km long Tjukalka. It flows through after a few kilometers the 118 km ² Tenissee, which is connected to the west neighboring 146 km ² Saltaimsee, as well as the small lake Atschikul (even this is given partly as the origin of Oscha ). From there, the Oscha flows increasingly meandering on each about one-third of their length in predominantly easterly, north-easterly and north- westerly direction last through the southern part of the West Siberian Lowland. You finally flows 13 km north- west ( downstream ) of the village and Rajonverwaltungszentrums Znamenskoye in the Irtysh.

The catchment area of the river comprises 21,300 km ². The Osha has few tributaries. The most important by far are the Ik (length 48 km) and the opening into the lower reaches of the Bolshoi Ajow ( " Big Ajow ", 266 km), both from the left.

The outflow at the village Schtscherbakowo, 43.4 km upstream of the mouth and above the mouth of about the same water-rich tributary Bolshoi Ajow, is an annual average 4.95 m³ / s, with a maximum monthly average of 20.01 m³ / s in May and a minimum monthly average of 0.87 m³ / s in March. From the end of October until the second half of April, the river freezes usual.

All along the river there are a number of smaller towns. The most important is the Rajonverwaltungszentrum Kolossowka. The upper and middle reaches follows the left bank of the regional road Tjukalinsk to Tara, the underflow is near the mouth of the regional road Tara - Tobolsk crossed.